1. Field of the Invention
This invention relates to a resume control system suitable for a personal computer having a resume function and also to a method used in the system.
2. Description of the Related Art
The development of semiconductor technology has enabled microprocessors and memory LSIs of high performance to be manufactured at very low cost. In particular, some of these microprocessors can simultaneously perform 8-bit processing, 16-bit processing, and 32-bit processing, and hence can process data at high speed. The following products, made by Intel Co., Ltd in the U.S.A., and generally used in personal computers, are listed as such microprocessors: iAPX86 (8086), iAPX88 (8088), iAPX186 (80186), iAPX286 (80286), and iAPX386.
The iAPX286, for example, can operate in two modes, i.e., real address mode and protective virtual address mode. In the real address mode, a memory having a capacity of less than 1 MB can be accessed, and the programs made for iAPX86 or iAPX186 also can be executed without being modified. In the protective virtual mode, a memory having a capacity of 1 MB or more can be memories such as a virtual memory. The protective virtual mode and real address mode are determined by setting and resetting a protection enabling bit provided in the iAPX286, respectively.
The memories are addressed by the use of segment registers and offset registers in the real address mode, and addressed by the use of global descriptor tables (GDT), segment selectors, and offset registers, in the protective virtual address mode.
A personal computer, using the iAPX286 and having resume function, has been developed in recent years.
Heretofore, most application programs were prepared using microprocessors prior to the introduction of the iAPX286 microprocessor. In recent years, however, various application programs which are executed in the protective virtual mode are being prepared. Accordingly, there is a desire to be able to effect the resume function in the protective virtual address mode as well.
However, the conventional resume processing programs can be executed in the real address mode only. As is described above, the memories are addressed in different ways between the real address mode and protective virtual address mode. Accordingly, these conventional programs cannot be executed in the protective virtual address mode, unless they are modified. Alternatively, it costs a lot to
However, a complicated control would be required in order to allow a resume processing program adapted for execution in the real address mode to also be effective in the virtual address mode. prepare respective resume processing programs for the real address mode and protective virtual address mode.
The present invention is related with the inventions disclosed in the following U.S. Patent applications assigned to the present assignee.
U.S. Pat. application No. 343,356 filed Apr. 26, 1989 (Title: Method and System for Resuming Data Processing in Computer; Inventor: Toshimitsu SAITO) discloses a method and a system for resuming data processing. In this method, the resuming mode is set after the computer system is bootloaded. When the power switch is turned off, the power source generates a power switch-off signal. In the resume mode, the system data is stored in a file upon detection of the power switch-off signal. After a predetermined period of time has elapsed from the switch-off, or if a signal is generated for indicating that the storage of the system data has been completed, the power is cut off. When the power switch is turned on again, the initialization of memories and the like, and the system data stored in the file are read out of it, and then restored in the memories. Thus, the data processing can be resumed in the state of the system having been assumed immediately before the power switch was turned off.
U.S. Pat. application No. 507,490 filed Apr. 11, 1990 (Title: Computer Having Resume Function; Inventor: Shizuka GUNJI) discloses a computer having a resume function. In this system, it is first selected whether or not to enable the resume function, and whether or not to check a password. If it is selected to enable the resume function, and to check the password, the data processing system commands that one should input the password upon turning on the power switch. When the password is input by the use of the keyboard or the like, the data processing system performs resume processing. If the correct password is not input, the resume processing is inhibited, which prevents the stored data from being known or broken into by a third party.
U.S. Pat. application No. 540,643 filed Jun. 19, 1990 (Title: Computer Having A Resume Function And Operable On An Internal Power Source; Inventors: Toshimitsu SAITO; Junko KONNO) discloses a computer having a resume function and operable by a battery, which incorporates a circuit for checking voltage output from the battery, and a control circuit. If the voltage output from the battery is reduced lower than a predetermined value during processing, the resume processing is executed to protect data, irrespective of whether or not the resume mode is set, thereby storing the data processing then having been executed. When the output voltage of the battery is returned to more than the predetermined value, the data processing is resumed from the interrupted state.
U.S. Pat. application No. 549,934 Title: Method And System For Performing Display Data Resuming Process; Inventor: Makoto ARAI; Priority Date: Jul. 11, 1989) discloses a method and a system for executing the resume processing of display data. This method is applied to a personal computer having no backup batteries for a display memory owing to restrictions in the design of the hardware. The power switch is turned off after the data stored in the display memory is stored in the backup memory of a system memory having its own backup battery. When the power switch is turned on again, the display data stored in the backup memory is restored in the display memory. In this way, the display data, stored in the display memory immediately before the turn-off of the power switch, can be restored in the display memory.